CVE-2024-53058 Information

Description

In the Linux kernel the following vulnerability has been resolved:

net: stmmac: TSO: Fix unbalanced DMA map/unmap for non-paged SKB data

In case the non-paged data of a SKB carries protocol header and protocol payload to be transmitted on a certain platform that the DMA AXI address width is configured to 40-bit/48-bit or the size of the non-paged data is bigger than TSO_MAX_BUFF_SIZE on a certain platform that the DMA AXI address width is configured to 32-bit then this SKB requires at least two DMA transmit descriptors to serve it.

For example three descriptors are allocated to split one DMA buffer mapped from one piece of non-paged data: dma_desc[N + 0] dma_desc[N + 1] dma_desc[N + 2]. Then three elements of tx_q->tx_skbuff_dma[] will be allocated to hold extra information to be reused in stmmac_tx_clean(): tx_q->tx_skbuff_dma[N + 0] tx_q->tx_skbuff_dma[N + 1] tx_q->tx_skbuff_dma[N + 2]. Now we focus on tx_q->tx_skbuff_dma[entry].buf which is the DMA buffer address returned by DMA mapping call. stmmac_tx_clean() will try to unmap the DMA buffer ONLY_IF tx_q->tx_skbuff_dma[entry].buf is a valid buffer address.

The expected behavior that saves DMA buffer address of this non-paged data to tx_q->tx_skbuff_dma[entry].buf is: tx_q->tx_skbuff_dma[N + 0].buf = NULL; tx_q->tx_skbuff_dma[N + 1].buf = NULL; tx_q->tx_skbuff_dma[N + 2].buf = dma_map_single(); Unfortunately the current code misbehaves like this: tx_q->tx_skbuff_dma[N + 0].buf = dma_map_single(); tx_q->tx_skbuff_dma[N + 1].buf = NULL; tx_q->tx_skbuff_dma[N + 2].buf = NULL;

On the stmmac_tx_clean() side when dma_desc[N + 0] is closed by the DMA engine tx_q->tx_skbuff_dma[N + 0].buf is a valid buffer address obviously then the DMA buffer will be unmapped immediately. There may be a rare case that the DMA engine does not finish the pending dma_desc[N + 1] dma_desc[N + 2] yet. Now things will go horribly wrong DMA is going to access a unmapped/unreferenced memory region corrupted data will be transmited or iommu fault will be triggered :(

In contrast the for-loop that maps SKB fragments behaves perfectly as expected and that is how the driver should do for both non-paged data and paged frags actually.

This patch corrects DMA map/unmap sequences by fixing the array index for tx_q->tx_skbuff_dma[entry].buf when assigning DMA buffer address.

Tested and verified on DWXGMAC CORE 3.20a

Reference

https://git.kernel.org/stable/c/ece593fc9c00741b682869d3f3dc584d37b7c9df https://git.kernel.org/stable/c/a3ff23f7c3f0e13f718900803e090fd3997d6bc9 https://git.kernel.org/stable/c/07c9c26e37542486e34d767505e842f48f29c3f6 https://git.kernel.org/stable/c/58d23d835eb498336716cca55b5714191a309286 https://git.kernel.org/stable/c/66600fac7a984dea4ae095411f644770b2561ede